The claims of a terrorist plot to blow up New York subways made public last week were not substantiated, administration and federal law enforcement sources confirmed to FOX News on Tuesday.

The sources said the last of the threat information made public by New York City officials last week was checked out by Saturday night and "none of the claims were substantiated," the sources said.

Officials last week said they were still investigating claims by a federal intelligence agency informant that Al Qaeda (search) operatives in Iraq had schemed to attack the subways using baby strollers and briefcases packed with remote-control detonated explosives as early as Oct. 7.

They also continued to defend a decision to flood the subways on Oct. 6 with thousands of extra police officers. Three suspects in Iraq were arrested and interrogated about the potential threat.

After four days of high alert on the subway systems, city officials on Monday announced they were scaling back on security operations on the trains and in the train stations.

The administration official told FOX News on Tuesday that "there was a lot of doubt" about the informant who led the U.S. military to the three suspects in Iraq. The informant who had been credible in the past and was known to the Defense Intelligence Agency appears to have pulled some of the names and information "out of nowhere," sources told FOX News.

Authorities said they're now satisfied that the three suspects arrested in Iraq last week are not Al Qaeda members, as the informant indicated. They also have never been to an Afghan terror training camp and are not pharmacists, as was originally alleged by the informant, according to both sources.

The federal law enforcement source even suggested that the informant's motivation may have been financial, since he had been paid in the past for information.

Police Commissioner Raymond Kelly (search) on Monday stressed that police would continue random bag searches and other precautions in the subways that were launched in the summer in response to the bombings of the London transit system (search).

John Miller, an assistant FBI director and the agency's chief spokesman, said federal authorities agreed with the police department's assessment that any potential risk had subsided.

Miller said the operation in Iraq "would have served to neutralize any threat that may or may not have existed."

The suspects in custody in Iraq denied they planned to coordinate with operatives who were already in the city to carry out an attack, said two law enforcement officials. The men had passed polygraph tests, the officials added.

"The people supposedly standing by in New York probably were never there," one of the officials said. Both officials spoke on condition of anonymity because the investigation had not been completed.

Still, city officials stood by their decision to heighten subway security, saying the initial tip had come from an informant with a reputation for reliability, and was too specific to ignore.

"We did precisely the right thing," Kelly said. "We had no choice but to respond the way we did."

FOX News' Catherine Herridge and The Associated Press contributed to this report.